1. Field of the Invention
The present invention relates to a printing system for direct printing using digital data.
2. Description of the Background Art
In a printing press for printing a large number of products, printed sheets are ejected into a stocker attached to the printing press and then transported for post-processing such as a bookbinding process.
The printing press is capable of printing on sheets of paper having a variety of sizes. When the stocker receives an accumulation of printed sheets of difference sizes, for example, by the ejection of a large number of A4 printed sheets followed by a large number of A3 printed sheets, a sheet stack falling apart accident is liable to occur in the stocker.
To prevent such an accident, it is desirable to do printing on successive sheets of as uniform sizes as possible when printed sheets are to be accumulated. The uniformity of the sizes of the sheets prevents the occurrence of the sheet stack falling apart even in the case of the accumulation of a large number of printed sheets in the stocker.
To prevent the sheet stack falling apart accident, there has been a printing press having the function of prompting a user to remove previously printed sheets, if accumulated in the stocker, out of the stocker before printing on sheets of a size different from the size of the previously printed sheets.
Many of the conventionally used printing presses are printing presses using plates, i.e., those of the type in which a colorant such as ink is applied to the plates for formation of a print image for printing. In such a conventional printing press, printing on sheets of a size different from that of the previously printed sheets requires the exchange of the plate previously used for printing for another. The printing press must be inevitably stopped during the time for the plate exchange. It is hence possible to spare time for removing the accumulated sheets out of the stocker while the printing press is stopped.
The present invention is intended for a printing system for continuously printing products of different sheet sizes.
According to the present invention, the printing system comprises: a) a printing apparatus including a-1) a printing section for continuously printing a plurality of print data on a plurality of sheets of paper to provide a plurality of printed sheets, a-2) a stock section including at least one stocker, and a-3) an ejecting mechanism for ejecting the plurality of printed sheets into the stock section; and b) a controller including b-1) an acquiring element for acquiring print sizes corresponding respectively to the plurality of print data, b-2) a comparing element for making a comparison between the print sizes, and b-3) a control element for controlling the printing section and the ejecting mechanism based on a result of the comparison by the comparing element to provide a stable stack including printed sheets of different sheet sizes in the stock section.
Preferably, the print sizes of the print data to be continuously printed are compared with each other. If the print size of print data to be printed later is greater by at least a predetermined value than the print size of printed sheets stored in the stocker, a printing process is suspended, and an operator is prompted to remove the printed sheets out of the stocker; otherwise the destination of the printed sheets for the print data to be printed later is changed to another stocker capable of storing the printed sheets.
This avoids the falling apart of stacks of printed sheets due to the accumulation of a stack of printed sheets of a greater sheet size on a stack of printed sheets of a smaller sheet size.
In accordance with one aspect of the present invention, the controller comprises: a sorting element for sorting the print sizes of the plurality of print data to determine printing order, based on the result of the comparison between the print sizes by the comparing element; and an element for controlling the printing section to print the plurality of print data in the printing order.
This gives precedence to the printing of the sheets having a greater print size to prevent stacks of printed sheets from falling apart.
It is therefore an object of the present invention to avoid the falling apart of a stack of printed sheets of different sizes accumulated.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.